6. (a) Which of these is a vector? A) energy B) force C) mass D) work (b) (i) State the equation that relates acceleration to change in velocity and time taken - Edexcel - GCSE Physics Combined Science - Question 6 - 2020 - Paper 1

The equation that relates acceleration to change in velocity and time is given by:

$a = \frac{\Delta v}{\Delta t}$ where $\Delta v$ represents the change in velocity and $\Delta t$ represents the time taken.

To calculate the acceleration of the van, we first determine the change in velocity:

$\Delta v = v_f - v_i = 20 \, \text{m/s} - 2 \, \text{m/s} = 18 \, \text{m/s}$

Now, using the equation for acceleration:

$a = \frac{\Delta v}{\Delta t} = \frac{18 \, \text{m/s}}{12 \, \text{s}} = 1.5 \, \text{m/s}^2$

Therefore, the acceleration of the van is $1.5 \, \text{m/s}^2$.

The distance traveled can be calculated by finding the area under the velocity-time graph. The area under the graph represents the distance covered, which can be calculated as:

$$\text{Distance} = \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 15 \, \text{s} \times 7 \, \text{m/s} = 52.5 \, \text{m}$$

Thus, the cyclist travels a distance of $52.5 \, \text{m}$ in the 15 s.

The stopping distance of a car is influenced significantly by driver factors, including:

• Reaction Time: A driver’s reaction time can vary based on alertness. A distracted or tired driver may take longer to react to a hazard, increasing the stopping distance.
• State of Mind: If a driver is under the influence of drugs or alcohol, their judgment and reflexes are impaired, thereby increasing stopping distance.

For instance, a driver who is tired may not react timely to a red light, leading to an extended stopping distance.

Factors related to the car or the road that affect stopping distance include:

• Tires: Worn or under-inflated tires can decrease traction, causing longer stopping distances.
• Brakes: The condition of the brake system impacts stopping capability. Worn brakes may not apply adequate force.
• Road Conditions: Wet or icy roads decrease friction between the tires and the surface, leading to increased stopping distances.

For example, if a car is on a slick road, its stopping distance can be significantly greater than on a dry road.